This invention is directed to a method and means for optimizing muscular activity between the jaws as applied to a dental crown seating device for use during seating and cementing of dental crowns and bridges, which method and device mediates, maximizes, and transfers pressures transmitted through the teeth of opposing arches by the muscles of mastication as they contract to supply biting pressure utilized for the seating and cementing of dental crowns.
Whenever a dental patient requires placement of an artificial dental crown, or multiple crowns with artificial teeth interposed, known as bridges, such crowns and bridges must be cemented into position after manufacture. The crown or bridge is first placed over the tooth stump or stumps for which it was made and forced completely on to the stump under pressure, a process known as seating, to assure proper fit. For purposes of this application and clarity, the word "appliance" will be used to represent all of the various types of crowns and bridges, and will be used in the singular, although it should be understood that the crowns, artificial or natural, and the tooth stumps, may be singular or plural in the individual case. The trial-seated appliance is then removed from the stump, cleaned, dried, and internally coated with dental cement. It is then re-seated on the tooth stump. The patient is then required to bite forcefully against the seated appliance with sufficient pressure to hold it in position against the opposing hydraulic pressure of the cementing medium. This biting pressure should be maintained, without substantial change or movement of the jaws, for such period of time as is necessary for the dental cement used to undergo the chemical-mechanical change required for it to permanently harden and bond the appliance to the tooth stump. Prior art has dictated the use of wooden sticks, rolls of cotton, and various other devices to interpose between upper and lower teeth for the purpose of transmitting biting pressure from the muscles of mastication. While these prior art devices have been useful, they all have substantial problems in use. The major problem is that the jaw muscles tire rapidly, the patient is not able to maintain strong, steady biting pressure, and is forced to relax the muscles. The reason for this is that, as the muscles reach exhaustion, the patient experiences muscular discomfort. With growing discomfort, the patient discontinues biting pressure in order to ease the growing muscular discomfort and to rest. With the discontinuation of biting pressure, and relaxation of the muscles, the jaws also open to help further relax the muscles and ease discomfort. After thus relaxing and resting, the patient again closes the jaws and resumes firm biting pressure, only to quickly tire and relax again. Under these conditions, the appliance, and the internal layer of cement, is subjected to repeated periods of pressure and release of pressure. The appliance is seated against the stump each time by biting pressure. As the patient rests momentarily, pressure is released and the jaws separate. With the release of pressure and separation of the teeth, the internal hydraulic pressure of the viscous unhardened cement that now fills the space between the tapered tooth stump and the similarly tapered inner wall of the appliance, forces the appliance away from the tooth stump. Thus, the appliance is "pumped" up and down, repeatedly, each time the patient's jaw muscles tire and the consequent discomfort forces the patient to relax the muscle pressure to rest, even momentarily. This repeated movement of the appliance on and from the tooth stump interferes with normal hardening of the cement, prevents the cement from hardening uniformly, and increases the time required for cement hardening. These result in a weakened bond between tooth-stump and appliance, a poorer fit, and greatly shorten the useful life of the appliance. The health of the tooth stump is also threatened as the weakened cement is lost over time, and the resultant separation between tooth stump and appliance wall offers ideal conditions for hidden decay to occur. This invention recognizes a problem hitherto unrecognized or dealt with: that the rapid tiring of the jaw muscles that causes the previously referred to problems in seating and cementation is not just normal muscle tiring from exertion, but that this muscle-fiber exhaustion is brought about because the muscle-fibers are extended or stretched prior to and during contraction, and so are incapable of optimal performance. The same holds true if the fibers are compacted before and during use: pre-straining the muscle-fibers by stretching or compacting them, and maintaining that strain during muscular activity, greatly limits both the magnitude and duration of muscle perfpormance. It must be further recognized that the prior art has other problems associated with its use. Bite-sticks are frangible and too hard on initial contact, with negligible resilience. The delicate periodontal membrane between tooth root and bony socket is thus crushed repeatedly each time the patient bites down. In the same manner as biting on an unexpected bit of bone causes shock and distress to the tooth of the diner, biting against the hard stick shocks the teeth and periodontal ligament. However, because the teeth and their supporting tissues are usually anesthetized, the patient feels no pain, and even though damage is being done, neither patient nor dentist is aware of it at the time. Cotton rolls are extremely soft and very springy. As the patient bites against them, there is little or no resistance felt by the teeth. As the cotton is compacted by stronger biting pressure to where some resistance is noticeable, the compacted cotton remains springy, with continual variations of pressure and springiness over this range of compaction. This gives the patient a very poor and constantly varying pressure feedback reference against which to judge muscle effort in order to maintain the required steady, firm, and prolonged biting pressure required. Further, as very strong pressure is applied, the cotton compacts still more, to a thickness that brings about compaction of the muscle-fibers, stressing these fibers still more during their exertion, to the detrimental effects mentioned previously. What is more, as the cotton becomes wet with saliva, it compresses even more, compounding this effect. Other prior art devices have these same defects, singly or multiple, depending on their construction. These have been hitherto unrecognized problems of the prior art which individually and collectively prevent the dental patient from providing the steady, sustained, firm biting pressure required to provide proper conditions for seating and cementation of dental appliances. What is needed is a method and means for maximizing inter-jaw muscle activity, in duration and magnitude, to that required for seating and cementing dental appliances, and for the effective transfer and maintenance of such developed pressure under physiologically benign conditions to the tooth stump, cement and appliance.